SHREWSBURY — The owner of some of the most popular cable television networks threatened to black them out at midnight Monday if Shrewsbury Electric and Cable Operators and other small cable company operators don't agree to a large increase in fees.

The five-year contract between SELCO and Viacom, an entertainment content company that owns the programming rights to networks such as Nickelodeon, Comedy Central and MTV, expired at midnight.

The National Cable Television Cooperative is negotiating a new contract on behalf of SELCO and more than 800 other small independent cable company operators that have approximately 5.2 million subscribers nationwide. The only others affected in Massachusetts are in Norwood and Braintree.

Contract negotiations have been contentious because of an increase Viacom wants in the first year of the contract, said Michael Hale, SELCO's general manager.

"It's an increase that we've never experienced the magnitude of," Mr. Hale said. "What they're asking for is 40 times the rate of inflation. It's equivalent to a gallon of gas going from $3.50 to $6 overnight. We're not willing to pay that increase. SELCO would have no means than to pass along those costs to the customers." Cable operators are prohibited from releasing specific details of the negotiations.

Mr. Hale said Viacom sent a letter threatening to black out its networks, including the 15 channels received by the 10,500 expanded basic subscribers in Shrewsbury. About 1,000 subscribers, who receive basic cable, would not be affected.

Jackie Pratt, marketing and customer care manager for SELCO, said this is the first time Viacom has made such a threat. SELCO has dealt with Viacom since the 1980s. She said that in the past the media giant has allowed the programming to continue as long as negotiations were proceeding in good faith.

"We've had many negotiations where we've gone past the original expiration date of the contract. But this is the first time a blackout is being threatened by a company we're working with," she said. "They're using the tactic of a possible blackout to turn our customers against us and say it's our fault."

She said Viacom is running a scroll at the bottom of its channels, saying the cable company operators want to drop their channels.

One scroll on Nickelodeon read, "Tonight, your cable provider will drop this channel and up to 23 more. And, they're refusing to negotiate. Call your cable provider today and tell them not to drop your favorite channels."

"It's a mischaracterization. It gives the opinion we wish to drop the channels and that is not true," Ms. Pratt said.

She said every cable company will have to go through similar negotiations with Viacom and eight other network conglomerates that own 90-plus percent of all video content. In 2012, Viacom blacked out its programming on DirecTV because of a fee dispute.

Mr. Hale said when SELCO increased cable television rates by about 5 percent effective April 1, SELCO officials had no idea Viacom would propose such an increase. He said the officials of the media giant are asking for huge increases simply because they can.

"The cost of programming is going through the roof. This is indicative of that," he said. "To me it's outrageous and egregious. I wonder how far can the programmers go before the consumers revolt."

He said he has written to U.S. Rep. James P. McGovern, D-Worcester, asking him to contact Viacom and find out why it is increasing fees at this rate. He said subscribers will be kept informed via social media. Subscribers are also advised to go to tvonmyside.com, which has alternative ways to get the lost programs if they go dark.